nrpe: let us specify timeout of check_nrpe

nrpe::monitor_service() define now let us pass a timeout parameter which
ends up being passed to the check_nrep utility as -t.  That raise the
default 10 seconds timeout which is useful for test we know to take a
bit longer than that.

The icinga command nrpe_check now require a second argument (the
timeout). It is only invoked from the nrpe::monitor_service define so I
guess it is not going to break anything.

One can later on raise the timeout of a check by doing something like:

 nrpe::monitor_service( 'check_job_queue': timeout => 30 )

Change-Id: Id031c71ac18ba1bc19f04832edad655694406095